The current work aims at achieving a better understanding of the cariogenic process through the study of determining factors involved in the formation of incipient caries. Enamel demineralization is being studied in in vitro systems using models based upon the driving forces derived from the solubility of various calcium phosphates involved, the transport processes in the enamel tissue, and the changes brought about on both of them by a) isomorphic substitutions in the enamel mineral, b) presence of tooth integuments (of a salivary origin), and c) composition of the fluid in contact with the dental tissue. The enamel demineralization is monitored by quantitative microradiography and by changes in pore volume distributions derived from water vapor sorption isotherms. Ongoing work on this subject and related areas comprises a) isolation of salivary constituents relevant to the formation of tooth pellicle, b) adsorption mechanisms of these constituents onto apatitic surfaces, c) effect of salivary pellicles upon transport of matter through the enamel tissue and upon the onset of demineralization by cariogenic microorganisms, d) reversibility of incipient caries and optimal conditions to accomplish it and 3) factors affecting the crystal growth of apatites under simulated biological conditions. BIBLOGRAPHIC REFERENCES: R. R. Zahradnik and E. C. Moreno. Structural features of Human Dental Enamel as revealed by isothermal water vapour sorption. Archs. Oral Biol. 20, 317-325 (1975). E. J. Burke and E. C. Moreno. Diffusion fluxes of tritiated water across hHman Enamel Membranes. Archs. Oral Biol. 20, 327-332 (1975).